Transcript Chapt. 1.1 Using Variables Modeling Relationships with Variables • A variable – a symbol, usually a letter, that takes the place of one.

Chapt. 1.1 Using Variables
Modeling Relationships with Variables
• A variable – a symbol, usually a letter, that
takes the place of one or more numbers.
• An algebraic expression – a mathematical
phrase that can include numbers, variables,
and operation signs.
– Sometimes called variable expressions.
Writing an Algebraic Expression
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More than – addition
Less than, difference of – subtraction
Product of – multiplication
Quotient of – division
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Writing an Algebraic Expression
Write an Algebraic Expression for each phrase.
a. Eight more than n.
- add the first number, eight, to the second number, n.
Answer: n + 8
b. The difference of n and 8.
- subtract 8 from n.
Answer: n – 8
c. The product of 7 and n.
- multiply 7 and n.
Answer: 7n
d. The quotient of n and 7.
- divide n by 7.
Answer:
n
7
Writing an Algebraic Expression Cont.
• Define a variable and write an algebraic
expression for each phrase.
a. Two times a number plus nine.
Define: Let x = the number
Answer: 2x + 9
b. Five less than three times a number.
Define: Let m = the number
Answer: 3m – 5
More Practice!!!! P. 6 # 1 – 7 odd
• Write an algebraic expression for each phrase.
1. 4 more than p.
4+p
3. 12 minus m.
12 - m
5. The quotient of n and 8.
n
8
7. 23 less than x.
x – 23
More Practice (Cont.)!!!! P. 6 # 9 – 15 odd
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Define a variable and write an expression for each
phrase.
9. 2 more than twice a number.
Let m = a number
2m + 2
11.9 minus a number.
Let n = a number
9-n
13. The product of 5 and a number.
Let k = a number
5k
15. The quotient of a number and 6.
s
Let s = a number
6
Modeling Relationships with Equations and
Formulas
• Use algebraic expressions to write an equation.
– An equation – a mathematical sentence that uses
an equal sign.
• If an equation is true, the two expressions on either side
of the equal sign represent the same value.
Modeling Relationships with Equations and
Formulas (cont.)
• Example.
– CDs cost $10 each. Write an equation for the total
cost of a given number of CDs.
• Let n = number of CDs bought
• Let c = the total cost
– ANSWER: c = 10 • n
c = 10 n
Homework!!!
• Textbook – p. 6 # 2 – 20 even